[media] v4l: vsp1: dl: Don't free fragments with interrupts disabled

Freeing a fragment requires freeing DMA coherent memory, which can be
performed with interrupts disabled as per the DMA mapping API contract.
The fragments can't thus be freed synchronously when a display list is
recycled. Instead, move the fragments to a garbage list and use a work
queue to run the garbage collection.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>